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PETRELS (PROCELLARIIDAE; 8+ SPECIES) Worldwide family of mostly

medium-size, superficially gull-like seabirds with long narrow wings, webbed feet, hook-tipped

bills with nostrils encased in a tube at top. Ages/sexes similar. Mostly silent at sea. No species

breeds in Costa Rica.

WEDGE-TAILED SHEARWATER  Ardenna pacifica 43–47cm, WS 99–109cm.

Commonest large shearwater off Pacific coast, but rarely seen from land.

Locally in flocks of 100s that mix in feeding and rafting flocks with boobies,

terns, other shearwaters. In calm, flight typically unhurried with wings pressed

forward slightly and crooked; wingbeats shallow and easy, interspersed with

glides on slightly arched wings; wheels higher in strong winds but usually not

steeply. Most birds white-bodied but small numbers of dark morphs occur.

Note light build with small head, relatively broad crooked wings, long tapered

tail, grayish bill (small numbers of both morphs have pinkish bill with darker

tip); cf. bigger and bulkier Pink-footed Shearwater. STATUS: Fairly common to common nonbr. migrant,

mainly Nov–Apr, smaller numbers May–Oct. (Tropical Pacific and Indian Oceans.)

PINK-FOOTED SHEARWATER  Ardenna creatopus 45–48cm, WS 110–118cm.

Pacific, offshore. Singles or small groups passing by, or mixed with flocks of

Wedge-tailed Shearwaters. Typically flies with languid wingbeats and easy

glides; can wheel high and steeply when windy. Larger and bulkier than Wedge-

tailed with bigger head, broader wings held less crooked in flight, shorter and

broader, less tapered tail; note pink bill with black tip. Underparts and

underwings white overall with variable dusky markings, rarely mostly dusky.

STATUS:  Uncommon to rare nonbr. migrant, mainly Apr–May, Sep–Nov.

(Breeds Dec–May in Chile, migrant to NE Pacific.)

PARKINSON’S PETREL  Procellaria parkinsoni 41–46cm, WS 112–123cm.

Pacific, offshore. Large dark petrel that scavenges at fishing boats; likely to be

found as singles or small groups, not usually with rafts of shearwaters. Flies with

easy smooth wingbeats and buoyant glides in calm to light winds, with

wheeling glides and bouts of loose flapping in moderate winds. Distinctive,

with very dark plumage, pale creamy bill with dusky to blackish tip, black

legs and feet. STATUS: Scarce to seasonally uncommon nonbr. migrant, mainly

Mar–Oct, usually well offshore. (Breeds Nov–May in New Zealand, migrant to

tropical E Pacific.)

GALAPAGOS PETREL  Pterodroma phaeopygia 39–42cm, WS 99–110cm.

Paci­fic, offshore. Distinctive, medium-large petrel with long narrow wings,

tapered tail, variable dark hood, and boldly patterned underwings. In light winds,

flies with languid wingbeats and long shearing glides on slightly bowed wings; in

stronger winds, wheels and banks but not steeply, with little flapping. Sometimes

associates with feeding flocks of boobies, terns, shearwaters. STATUS:  Scarce

nonbr. migrant, possible year-round, usually well offshore. (Breeds year-round in

Galapagos, ranges in tropical E Pacific.)

TAHITI PETREL  Pseudobulweria rostrata 38–42cm, WS 101–108cm. Pacific,

offshore. Distinctive, fairly large petrel with very long narrow wings, tapered

tail, very stout black bill; note white body contrasting with dark underwings

(sometimes showing paler median stripe). In light winds, flies with languid

wingbeats and long shearing glides on wings held out rather straight from body;

in stronger winds, wheels and banks but not steeply, with little flapping. Feeds

by scavenging, thus not usually with feeding flocks. STATUS: Scarce to uncommon

nonbr. migrant, mainly Mar–Nov, usually well offshore. (Tropical Pacific.)